Catalysts

Question 1

What 2 types of catalysts can there be?

Answer 1

= heterogeneous
= homogenous

Question 2

What are catalysts?

Answer 2

increases rate of reaction without being used up, reduces activation energy by providing an alternatuve route, allows more paticles to overcome activation barrier

Question 3

what are heterogenous catalysts?

Answer 3

= usually solids, whilst the reactahts are gaseous in a solution, reaction occurs at surface of catalyst
= different phase from the reactants

Question 4

How do these catalysts work? heterogenous

Answer 4

= reactants form bonds with atoms at active sites on the surface of the catalyst
= as a result, bonds in the reactants are weakened and break
= new bonds form between the reactants held close on the catalytic surface
= weakens the bonds between product and catalyst and product leaves

Question 5

How does surface area effect this?

Answer 5

= increasing the surface area of a solid catalyst improves its effecttiveness

Question 6

What catalust is used in the comtact process?

Answer 6

= V2O5 is the catalyst- remember these are never used up
= 2SO2 + O2 => 2SO3

Question 7

What is step 1 od rhe contact process?

Answer 7

= SO2 + V2O5 => SO3 + V2O4

Question 8

What is step 2 of the contact process?

Answer 8

= = 2V2O4 + O2 => 2V2O5

Question 9

How are catalysts posioned?

Answer 9

= catalysts can be posioned by impurities and reduces efficiency and may need to be replaced
= less product is made
= increaes cost of chemical proceses
=

Question 10

What are homogenous catalysts?

Answer 10

= when catalysts and reactants are the same state, the reaction uses an in intermediate that reacts to form producy and regenerates the catalyst

Question 11

What will the interediate tends to have?

Answer 11

= different oxidation states to the oriignal transition metal

Question 12

Why do transition metals make good homogemous catalysts?

Answer 12

= form various oxidation states, able to donate and recieve electrons

Question 13

What ar are the reactions between I- and S2O82- ?

Answer 13

S2O8 2- + 2I- => 2So4 2- + I2

Question 14

What are the 3 reactions that need to be leart?

Answer 14

S2O8 + 2e- => 2So4 2-
Fe3+ + e- => Fe2+
I2 + 2e- => 2I-

Question 15

Why is the uncatalustsed reaction vert slow?

Answer 15

= reaction needs a collision between 2 negative ions repulsiomeans there is a high activation energy

Question 16

What is the catalysed alternative route?

Answer 16

= S2O8 + 2Fe2+ -> 2So42- + 2Fe3+

= 2I- + 2Fe3+ => 2Fe2+ + I2